The present trend towards miniaturization of mobile communication devices demands for smaller electric and electro-acoustic components. BAW (BAW=bulk acoustic wave) components can be used in RF filters, e.g., in duplexers in front-end modules of mobile communication devices. A duplexer usually comprises a TX (transmission) and an RX (reception) filter. The TX filter and the RX filter are band pass filters with adjacent but different pass bands. An important factor determining the pass band of a BAW pass band filter is the thickness of piezoelectric material arranged between two electrode layers of a resonator of the filter and the mass loading of a resonator.
One type of conventional BAW duplexers has different piezoelectric material thicknesses for the TX filter and for the RX filter. Accordingly, the two filters are manufactured with different processes and on different carrier chips.
Another type of conventional BAW duplexers has additional mass, e. g. additional layers on the upper electrode, deposited on selected resonators to reduce their respective resonance frequency.
The method for manufacturing for both types are relative complex, expensive and susceptible to errors. In particular, conventional duplexers have TX and RX filters on different carrier chips what is contrary to the miniaturization efforts.
What is needed is a BAW component where two BAW layer stacks can be easily arranged on the same chip to obtain a miniaturized BAW filter and where the composition of the component allows improved manufacturing methods to increase the gain of good components. What is further needed is a lamination for a BAW component and a method for manufacturing such a BAW component.